The present invention relates to a method of determining the distance between an area under fire and the muzzle of the weapon by means of autoradiography of the irradiated firing residues on this area.
Determining the distance between a fire arm and the point of impact is a very important problem in criminal investigation. In doubtful cases of suicide, justifiable self-defense, or even when determining whether a specific hole was caused by the impact of a bullet, the immediate environment of the point of impact is a very important source to be investigated.
A large number of methods of identification of traces of shots are known; but, so far neither chemical analysis nor purely quantitative determination through neutron activation analysis (NAA) permit a satisfactory assessment of the distance to be made. Among other disadvantages, these methods do not operate in the non-destructive mode because the irradiated filters with the traces of shots had to be destroyed for measurement so that the spurious activity of the matrix was removed.
Autoradiography has already been used to identify impacts of bullets as such by irradiating a piece of material fired at and afterwards contacting it with X-ray film. This film was then processed into prints or radiographs, respectively. However, this type of investigation of the hole made by a bullet does not allow any conclusions to be drawn as to the range from which a shot was fired.